Hitherto, various fluorine-containing compounds have been proposed. The fluorine-containing compounds have the advantageous effects of having properties excellent in heat resistance, oxidation resistance, weather resistance and the like. The fluorine-containing compounds are used as, for example, a water- and oil-repellent agent and a soil resistant agent by utilizing the properties that the fluorine-containing compounds have low free energy, i.e., difficulty in adherence. For example, U.S. Pat. No. 5,247,008 describes finishing agents for textiles, leather, paper and mineral substrates, which are aqueous dispersions of a copolymer of a perfluoroalkyl acrylate or methacrylate, an alkyl acrylate or methacrylate and an aminoalkyl acrylate or methacrylate.
The fluorine-containing compounds which can be used as the water- and oil-repellent agent include a fluorine-containing polymer which comprises (meth)acrylate ester having a fluoroalkyl group as a constituent monomer. Various recent research results indicate that in view of the practical treatment of fibers with the surface treatment agent, the important surface property is not a static contact angle, but is a dynamic contact angle, particularly a reversing contact angle. That is, the advancing contact angle of water is not dependent on the carbon number of the fluoroalkyl side chain, but the reversing contact angle of water in the case of carbon number of at most 7 is remarkably low than that in the case of carbon number of at least 8. In correspondence to this, an X-ray analysis shows that the side chain crystallizes when the carbon number of side chain is at least 7. It is known that the actual water repellency has relationship with the crystallization of the side chain and that mobility of the surface treatment agent molecules is an important factor for expression of the actual performances (for example, MAEKAWA Takashige, FINE CHEMICAL, Vol. 23, No. 6, page 12 (1994)). Accordingly, it has been believed that the acrylate polymer having low carbon number of fluoroalkyl group in the side chain which is at most 7 (particularly at most 6) has low crystallinity so that the polymer cannot satisfy the actual performances (particularly water repellency).
Recent study results (EPA Report “PRELIMINARY RISK ASSESSMENT OF THE DEVELOPMENTAL TOXICITY ASSOCIATED WITH EXPOSURE TO PERFLUOROOCTANOIC ACID AND ITS SALTS” (http://www.epa.gov/opptintr/pfoa/pfoara.pdf)) and the like clarify that a PFOA (perfluorooctanoic acid) doubtfully has a potential risk of environmental load. EPA (Environmental Protection Agency of USA) announced on Apr. 14, 2003 that the EPA intensifies the scientific investigation on PFOA.
On the other hand, Federal Register (FR Vol. 68, No. 73/Apr. 16, 2003 [FRL-2303-8]) (http://www.epa.gov/opptintr/pfoa/pfoafr.pdf), EPA Environmental News for release Monday April, 2003 “EPA INTENSIFIES SCIENTIFIC INVESTIGATION OF A CHEMICAL PROCESSING AID” (http://wvvw.epa.gov/opptintr/pfoa/pfoaprs.pdf), and EPA OPPT FACT SHEET Apr. 14, 2003 (http://www.epa.gov/opptintr/pfoa/pfoafacts.pdf) announced that a “telomer” may possibly metabolize or decompose to PFOA. It is also announced that the “telomer” is used in a large number of commercial products including fire fighting foams, care products and cleaning products as well as soil, stain and grease resistant coating on carpets, textiles, paper, and leather.
WO2010/030044 discloses a treatment composition comprising a fluorine-containing polymer which has repeating units derived from a fluorine-containing monomer, and a (meth)acrylate monomer having a cyclic hydrocarbon group. WO2011/122442 discloses a treatment composition comprising a fluorine-containing polymer which has repeating units derived from alpha-chloroacrylate, and a (meth)acrylate monomer having a hydrocarbon group. Strong water repellency is not studied in these gazettes.